Pulse-beacon transmitter circuit



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PULSE-BEACON TRANSMITTER CIRCUIT Filed June 20, 1952 To flNTEIl/Wl IN VEN TOR.

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United States Patent PULSE-BEACON TRANSMITTER CIRCUIT Edward Theordore Kurtzner, Jr., Woodlyn, Pa., assignor, by mesne assignments, to the United States of America as represented by the Secretary ofthe Navy 1 Application June 20, 1952, Serial No. 294,670

1 Claim. (Cl. 250-36) The present invention relates to high-frequency generators and more particularly to ultra-audion oscillator circuits capable of generating sustained high-frequency electromagnetic oscillations. While the present invention is subject to a variety of applications, it is particularly useful as an oscillatory-current generator for a very-high-frequency transmitter.

For some purposes, such as facilitating the recovery of landed balloon-borne instruments or in air-sea rescue Work, it is desirable to have an inexpensive light-weight transmitter that will operate in the very-high-frequency range for a definite period of time over a limited distance.

An object of the present invention is to provide a compact and inexpensive very-high-frequency transmitter capable of generating a sustained high-frequency electromagnetic oscillation. Another object of the present invention is to provide a high-frequency current generator in which an ultra-audion oscillator circuit is energized by spark-coil means to modulate the oscillator.

The invention will best be understood from the following description of a specific embodiment when read in conjunction With the accompanying drawing.

In the drawing, the transmitter consists of an oscillator circuit of the ultra-audion type wherein a three-electrode tube 1 has plate 23 and grid 27 elements connected by a tuned circuit. Said three-element tube is of the acorn type such as an RCA No. 958 and said tuned circuit is composed of a tank coil 3. Enough capacity is present between the turns of said coil 3 and the grid-to-plate capacity of said tube 1 to produce an efiicient tuned circuit. The size of said tank coil determines the frequency at which said oscillator circuit will operate.

The plate voltage to said tube is supplied by a spark or ignition coil. A battery 5 supplies power to said spark coil. Said battery also supplies the voltage for the filament 25 thereby eliminating the added weight and bulk of a B supply. Due to the rapidity at which the plate voltage is turned on and off, said tube can be operated at a much higher voltage than with continuous operation.

A capacitor 17 in the grid-to-plate circuit of said oscillator tube provides voltage feed back of the output circuit of said tube in the proper phase and magnitude to generate continued oscillations. Grid bias for said tube is provided by a resistor 13. An inductance choke 19 is connected between the grid of said tube and said bias resistor 13, and serves to isolate the oscillations of said oscillatory circuit from said power supply. Another choke 15 is inserted between the inductance coil 3 and the spark coil 9 and performs the same function as choke 19. A resistor 11 in the filament circuit provides filament bias for said tube. Load coil 21 is inductively coupled to coil 3 and constitutes the output circuit of the transmitter.

A breaker circuit 7 consists of a vibrating reed 29 and a fixed reed 31. Both of said reeds having breaker contacts attached thereto. The vibrating reed can be made out of steel or other suitable material and can be r- 2 19a saz Ice Iatented Ma y 7, 31957 2 so designed that its natural resonant frequency is of th order of 8,000 to 10,000 cycles. The frequency of said vibrating reed is determined by its length with'respect to its width and thickness. Said breaker contact is mounted on the end of said reed and can be made of tungsten. The vibrating reed is mounted at right angles to the soft, iron core of said spark coil. Said fixed reed is composed of non-magnetic metal and is so positioned with respect to said vibrating reed that its breaker contact touches the breaker contact of said vibrating reed forming a closed circuit when no voltage is applied.

It will be seen that when the voltage from said battery is applied to the circuit, current passes through said breaker contacts and into the primary of said spark coil. A magneticfield is built up around said soft-iron core attracting said vibrating reed and causing the breaker circuit to open. When said breaker circuit is open the magnetic field around the soft-iron core collapses and the vibrating reed returns to its normally closed position. Said reed will vibrate at its resonant frequency and de termines the recurrence rate of said transmitter. The frequency at which the reed 29 vibrates in the spark coil provides modulation for the oscillator and thereby eliminates the necessity of providing one or more tubes to provide this modulation. Because of the pulsing properties of the spark coil, the peak power output is greatly in excess of anything possible with a carrier Wave signal consistent with the specific requirements of this oscillator.

The type of antenna used in conjunction with said invention consists of two center-fed dipoles mounted at from each other and fed out of phase. This antenna arrangement produces a horizontally polarized 360 uniform field radiation from said transmitter.

From the discussion with reference to the diagram, it is observed that the spark coil is operated from the same battery that supplies the filament voltage thus eliminating the added weight and bulk of a B supply. Plate voltage to the oscillator tube is approximately 2,000 volts on peaks. The ratio of the time the oscillator is on compared to the time it is oil is about 1 to 20. The filament circuit is broken at the same time the plate voltage is applied. This produces an excess of electrons during the duty cycle of the oscillator. By pulsing the filament voltage it is possible to get a heavier cathode emission than under continuous operation. The adjustment of the space between breaker or vibrating contacts 7 controls the amount of current the oscillator draws and also controls the audio or modulating frequency of the oscillator.

In the present invention said vibrating contacts are adjusted so that the total drain on the batteries is 0.5 ampere. The vibrating reed producing the modulating tone of the transmitter can be set in the frequency range between 400 and 1000 cycles. The oscillator frequency is set at 180 megacycles and the input voltage is 4.5 volts.

To maintain a minimum weight and size of said transmitter the oscillator tube 1 is of the acorn variety. The coils and resistors selected are small in physical size. For example, coil 3 consists of three turns of #14 wire and is /2 inch long with a inch diameter. Coil 21 consists of two turns of #18 wire and is /4 inch long with a inch diameter. By choosing proper circuit elements the weight of the transmitter can be reduced to less than five pounds.

This invention is not to be construed as limited to the particular spark-coil means for energizing the oscillator circuit since this is regarded to be illustrative rather than restrictive.

What is claimed:

An oscillator circuit capable of producing a pulsed very-high frequency signal comprising a three-electrode tube having a plate, a grid and a cathode element, a

a 3 series circuit consisting of an inductance and capacitance connected between the plate and grid elements, a-step-up transformer connected to the plate and cathode elements, a breaker circuit including a vibrating reed and a fixed reed connected to said step-up transformer, and a direct current source of power connected to said cathode and plate'elernents simultaneously and intermittently, whereby the vibrating reed of said breaker circuit simultaneously energizs the plate and cathode elements of said tube and modulates the output of said tube. V

References Cited in the file of this patent UNITED STATES PATENTS Hupert et al Nov. 30; 1954 OTHER REFERENCES Radio Money Bag, in Radio & Television, January 1939, page 522. 

